1. Field of the Invention
The present invention relates generally to the cellular mechanisms and enzymes involved in the glycosylation of proteins manufactured by the cell. More particularly, the present invention involves altering the enzyme production capabilities of a cell in order to produce a soluble glycosyltransferase which is secreted by the cell and recovered for further use.
2. Description of Related Art
Glycosyltransferases are important enzymes which are essential to the cellular sunthesis of carbohydrates. The glycosyltransferases and their role in enzyme-catalyzed synthesis of carbohydrates are presently being extensively studied (43,44). These enzymes exhibit high specificity for forming carbohydrate structures of defined sequence. Consequently, purified glycosyltransferases are increasingly used as enzymatic catalysts in carbohydrate synthesis. Application of these enzymes has been limited because of difficulties in isolating and purifying them. As a result, glycosyltransferases are only available in very small amounts and are extremely expensive.
The isolation and purification of glycosyltransferases is difficult because of their low abundance in cells and because the enzymes are membrane-bound glycoproteins which reside in the Golgi apparatus of cells. Accordingly, the present purification procedures involve the use of animal tissues from which the enzymes must be extracted and purified. These purification procedures are not amenable to large scale production and therefore are not well suited to meet the present and future demands for purified enzymes to be used in research and in industrial applications involving synthesis of carbohydrates.
As a result, there is presently a need to provide methods for producing increased amounts of purified glycosyltransferases wherein the method is amenable to relatively large scale production of purified enzymes.